4 ms·

I remember sort of learning (just superficially) Z80 and 6502 assembly at the time (mid to late 80s) and thinking Z80 assembler was much simpler.

deleted 8y ago
[deleted]
setquk 8y ago
It is until you start treating the 6502 as a RISC CPU with 256 registers at 0x0000. I had that “ohhhhh” moment when I had a BBC master back in the late 80s. Zero page FTW. Z80 feels like wading in treacle after that. X86 is an abomination
znpy 8y ago
I can testimony for Z80 assembly (tough I cannot say anything about 6502). In high school one of our teachers made us program a Z80 board by hand. And when I say "by hand" I mean it quite literally: first a flow-chart, then a conversion to z80 assembly (two passes: pencil first, pen later), then datasheet at hand a conversion into z80 opcodes (this time it was three passes, the third one was to recalculate all jumps, absolute and relative ones). Last step was to input each opcode into memory by hand using an hexadecimal keypad. Then go to address 1800h, hold breath and press RUN. In retrospect, it was a very enlightening experience considering I and my school mates were like 16-17. But keep in mind, if a 17 years old can do this with relative ease (it was a technical high school, after all) that should tell you something about the simplicity and effectiveness of the Z80 instruction set. Z80 <3
- jacquesm 8y ago
  I bootstrapped a 6809 assembler by hand. That took a while :)
userbinator 8y ago
The 6502 is a much simpler CPU (3.5k transistors vs. 8.5k for the Z80), but the Z80 is easier to use and less limiting --- more registers and addressing modes, a stack not limited to 256 bytes and fixed location, and a more regular octal-format instruction encoding[1]. [1] http://www.z80.info/decoding.htm http://www.z80.info/decoding.htm
- namibj 8y ago
  What you call stack, I call register file.
  - jacquesm 8y ago
    Detected the Forth programmer.
    - namibj 8y ago
      No. I mean the overhead of loading from the register to the ALU is very small. I.e., this is an explicit cache in front of the 256-byte register file.
hyperpallium 8y ago
Some of this was due to syntax of their assembly languages. 6502 had letters for different addressing modes, whereas Z80 used parentheses for a memory lookup, e.g. LD A,(HL) uses HL as a pointer, loading its pointed-to value into A (IIRC). 6502 had more addressing modes, but some of them, if not all, could have used Z80 style syntax. After all, it would just be a different the assember (i.e. compiler) frontend, generating the same target machine code.

deleted 8y ago

[deleted]

setquk 8y ago

It is until you start treating the 6502 as a RISC CPU with 256 registers at 0x0000. I had that “ohhhhh” moment when I had a BBC master back in the late 80s. Zero page FTW. Z80 feels like wading in treacle after that. X86 is an abomination

znpy 8y ago

I can testimony for Z80 assembly (tough I cannot say anything about 6502). In high school one of our teachers made us program a Z80 board by hand. And when I say "by hand" I mean it quite literally: first a flow-chart, then a conversion to z80 assembly (two passes: pencil first, pen later), then datasheet at hand a conversion into z80 opcodes (this time it was three passes, the third one was to recalculate all jumps, absolute and relative ones). Last step was to input each opcode into memory by hand using an hexadecimal keypad. Then go to address 1800h, hold breath and press RUN. In retrospect, it was a very enlightening experience considering I and my school mates were like 16-17. But keep in mind, if a 17 years old can do this with relative ease (it was a technical high school, after all) that should tell you something about the simplicity and effectiveness of the Z80 instruction set. Z80 <3

jacquesm 8y ago
I bootstrapped a 6809 assembler by hand. That took a while :)

userbinator 8y ago

The 6502 is a much simpler CPU (3.5k transistors vs. 8.5k for the Z80), but the Z80 is easier to use and less limiting --- more registers and addressing modes, a stack not limited to 256 bytes and fixed location, and a more regular octal-format instruction encoding[1]. [1] http://www.z80.info/decoding.htm http://www.z80.info/decoding.htm

namibj 8y ago
What you call stack, I call register file.
- jacquesm 8y ago
  Detected the Forth programmer.
  - namibj 8y ago
    No. I mean the overhead of loading from the register to the ALU is very small. I.e., this is an explicit cache in front of the 256-byte register file.

hyperpallium 8y ago

Some of this was due to syntax of their assembly languages. 6502 had letters for different addressing modes, whereas Z80 used parentheses for a memory lookup, e.g. LD A,(HL) uses HL as a pointer, loading its pointed-to value into A (IIRC). 6502 had more addressing modes, but some of them, if not all, could have used Z80 style syntax. After all, it would just be a different the assember (i.e. compiler) frontend, generating the same target machine code.